The invention relates to surveying the geological formations through which a borehole passes, and more particularly to a method for characterizing their morphology relative to depth down the borehole.
If a physical characteristic such as resistivity is used for evaluating the formations traversed by a borehole, formations can be classified as a function of the following criteria: 1) a formation may be solid, i.e. it has resistivity values that are uniform, either resistive or conductive; 2) it may be non-solid, in which case it may be bedded if it has relatively rapid changes between resistive zones and conductive zones; 3) it may be heterogeneous, in which case it may be of the interwoven type comprising both resistive elements and conductive elements; 4) it may be of the type including resistive inclusions within a conductive background or; 5) it may be of the type having conductive inclusions within a resistive background.
Clearly, the morphological types of underground formations are related to their porosity and to their permeability. In hydrocarbon reservoirs, these parameters are determined to evaluate production potential. It is therefore advantageous to be able to characterize the morphology of formations in accordance with such a classification as specified above.